1. Field of the Invention
The present invention relates to a thermosensitive transfer film for use in forming a fluorescent substance layer in a display device such as a color cathode-ray tube and a method of manufacturing a display device.
2. Description of the Related Art
In recent years, as a display device comprising a color cathode-ray tube is progressively becoming large in size and its picture screen also is progressively becoming flat, a demand of improving contrast and color purity of a display device is increasing more from a quality standpoint. As an arrangement that can improve contrast of a display device, there has been proposed a method of providing a color filter layer corresponding to a fluorescent substance layer between a panel glass and the fluorescent substance layer (for example, the cited patent reference 1).
Since this color filter layer is disposed between the fluorescent substance layer of each color and the panel glass, although transmittance of light is lowered slightly, reflectance is lowered, and hence contrast ratio can be improved so that it is possible to improve color purity and contrast of the display device remarkably.
As a method of forming a color filter layer and a fluorescent substance layer on the inner surface of a panel glass, there have been proposed a slurry method and a transfer method. According to the slurry method, there is prepared slurry in which a material of a color filter layer of a fluorescent substance layer and a photosensitive component are dispersed. After this slurry has been coated on the inner surface of a glass panel, it is dried to form a layer. Further, the color filter layer or fluorescent substance layer with a predetermined pattern is formed by exposing and developing the resulting dried layer according to patterning.
On the other hand, the cited patent reference 2 discloses the transfer method. As is disclosed in the cited patent reference 2, there is prepared a thermosensitive transfer film having at least a photosensitive fluorescent substance layer, a color filter layer and a photosensitive adhesive agent layer formed on a base film. This thermosensitive transfer film is pressed against the inner surface of a glass panel by a suitable means by a roller, whereby the photosensitive fluorescent substance layer and the color filter layer are transferred to the inner surface of the glass panel and exposed and developed by patterning.
FIG. 1 of the accompanying drawings is a schematic cross-sectional view used to explain a thermosensitive transfer film according to the related art. Specifically, as shown in FIG. 1, this thermosensitive transfer film has a base film 60 serving as a supporting body on which a cushion layer 70 made of thermoplastic resin, a photosensitive fluorescent substance layer 50, a color filter layer 40 and a photosensitive adhesive agent layer 30 are formed, in that order. A cover film 80 is formed on the surface of the photosensitive adhesive agent layer 30 to protect the photosensitive adhesive agent layer 30. An antistatic layer 90 is formed on the rear surface of the base 90 in order to minimize static electricity produced when the thermosensitive transfer film is stripped from the base film 60.
[Cited Patent Reference 1]
Japanese laid-open patent application No. 64-7457
[Cited patent reference 2]
Japanese laid-open patent application No. 2001-43796
However, when the color filter layer and the fluorescent substance layer are transferred onto the inner surface of the glass panel by using such photosensitive transfer film, since this photosensitive transfer film is composed of many layers as described above, the film thickness increases unavoidably, and hence work efficiency of a transfer process is lowered. Also, when the photosensitive transfer film is exposed by patterning after the color filter layer and the fluorescent substance layer have been transferred onto the inner surface of the glass panel, exposure light has to pass through the fluorescent substance layer and the color filter layer until it reaches the photosensitive adhesive agent layer. During exposure light reaches the photosensitive adhesive agent layer through the fluorescent substance layer and the color filter, it is attenuated, and hence it becomes difficult to make sharp patterning.